Unexplained Visual Loss: Occult Macular Dystrophy

Abstract

A 32-year-old female presented with complaints of progressive blurred vision that has manifested since she was 18 years. She had a past medical history of harelip s/p repair in childhood. She had visited many hospitals since then. In 2008, she visited another medical center. According to her medical record, her best-corrected visual acuity was 6/30 in both eyes. Humphrey 30-2 was grossly normal (Fig. 54.1). Electroretinography (ERG) showed normal rod and cone responses in both eyes. Multifocal ERG revealed decreased central peaks in both eyes. The patient was suspected to have cone dystrophy, though no macular lesions could be found. She came to our clinic in 2013. Her best-corrected visual acuity remained 6/30 in both eyes. Anterior segments were normal with prompt pupillary light reflexes. Fundoscopic examination was normal for both eyes (Fig. 54.2). A full-field ERG showed normal rod and cone responses (Fig. 54.3), while a multifocal ERG showed decreased central peaks in both eyes (Fig. 54.4). Humphrey 10-2 demonstrated a small relative central scotoma in both eyes (Fig. 54.5). OCT showed a smear pattern of IS/OS segments in the central macula of both eyes (Fig. 54.6). The patient was suspected to have occult macular dystrophy. Peripheral blood DNA sequencing revealed a RP1L1 gene c.133 C > T mutation, which results in p.Arg45Trp of the RP1L1 protein. The diagnosis of occult macular dystrophy was confirmed, and the patient’s father was later found to carry the same mutation of the RP1L1 gene.